Samenvatting
In a simple theoretical model the location of two ring roads which minimises the total radial travel of a circular town of unit radius, is sought. It is assumed that drivers choose least time paths and that the speed of vehicles is controlled so as to minimize radial travel. It is shown that, whatever the distribution of origins and destinations, if an internal ring road minimises the total radial travel when the radial traffic flow just inside the ring equals the radial traffic flow just outside the ring.